dineen



g- 29, 1961 J. J. DINEEN 2,997,862

AIR CYCLE COOLING UNIT Filed Sept. 11, 1959 2 Sheets-Sheet 1 INTAKEINVENTOR 29,196] J. J. DINEEN 2,997,862

AIR CYCLE COOLING UNIFT Filed Sept. 11, 1959 2 Sheets-Sheet 2 lNVENTOREXPANSION CHAMBERS 2 g Ano RNEYS lNL-EE To EXPANEHONJ NUTLET FROM UnitedStates Patent 2,997,862 AIR *CYCLE COOLING UNIT John Drneen, EastNorthport, N.Y., assignor, by mesne assignments, to Chandler EvansCorporation, West Hartford, Conn a corporation of Delaware Filed Sept.11, 1959, Ser. No. 839,418 6 Claims. (Cl. 62-403) This invention relatesto an air cycle cooling unit,

and particularly such a unit designed for cooling the air in an enclosedspace such as the cab of a truck or the interior of a bus or other motorvehicle. It is an object of the invention to prOVide such a coolmg unitof improved efiiciency and compactness, with an expanson cylinder insidethe compression cylinder, the compression piston serving as theexpansion cylinder, with a combined piston ring and inlet valve, andwith other mechanical improvements.

It is a further object to provide a cooling unit in which the air to becooled is compressed, passed through an air-cooled heat exchanger,expanded, and supplied as relatively cold air to the interior of thetruck cab or other space.

It is another object to provide a cooling unit in which the outside airis drawn through the heat exchanger along a path generally counter tothe flow of the compressed air to be cooled, and passes also inheat-exchange relation to the wall of the compressor.

It is a further object to provide certain improvements in the form,construction, arrangement and materials of the several parts whereby theabove named and other objects may effectively be attained.

A practical embodiment of the invention is shown in the accompanyingdrawings, wherein:

FIG. 1 represents a vertical axial section through a completeone-cylinder unit in the plane of the drive shaft, parts of the heatexchanger cowling being shown in elevation and parts being broken away,the compressor piston being shown at the bottom of its stroke;

FIG. 2 represents a section as in FIG. 1, omitting part of the heatexchanger and showing the compressor piston substantially at the top ofits stroke;

FIG. 3 represents a transverse vertical section on the line IIIIII ofFIG. 1;

FIG. 4 represents a detail horizontal sectional view of the combinedpiston ring and inlet valve, taken on the line IVIV of FIG. 3, and

FIG. 5 represents, somewhat diagrammatically, a transversecross-sectional view of a plural-cylinder unit.

Referring to the drawings, the unit is shown as comprising a compressorblock 1 having a cylindrical compression chamber 2, spaced lowercrank-case portions 3, 4 and a valve block 5 within the uppercylindrical crankcase portion '5'. The drive shaft 6 is journaled at 7,8 in the outer walls of the portions 3, 4, 5' and passes through ahorizontal bore 6 in the block 5. The compressor piston 9 has adownwardly projecting inwardly cylindrical part 10 which constitutes thelateral wall of an expansion chamber 11, the top and bottom walls ofwhich are constituted by the under surface of piston 9 and the uppersurface of valve block 5. A suitable seal 12 is provided adjacent theupper periphery of block 5 and designed to bear against the innercylindrical surface of the part alt).

At diametrically opposite points on the outside of the part 10 aremounted the studs 13, alined with eccentrics 14 on the drive shaft, andconnecting rods 15 embrace saideccentrics and connect them to the studs13, with the provision of suitable anti-friction bearings between theconnecting rods and the eccentrics and studs.

The valve block is provided with four vertical bores, t e bores '16 and17 extending downward from the top of the block to the horizontal bore 6and having their axes in the same vertical plane with the axis of thedrive shaft 6, and the bores 18, 19 extending upward from the bottom ofthe block toward, but not to, the upper surface thereof, said latterbores being so located in the block that they do not intersect any ofbores 6, 16 and 17; certain connections being provided, however, asdescribed below.

The upper periphery of the bore 16 is beveled to form a seat for theexhaust valve 20, the stem 21 of which passes through the sleeve 22 andis provided with a yoke 23, axle pin 24 and cam-following roller 25. Thesleeve 22 is fixed in the bore 16 by means of a pin 26, and the roller25 is urged toward its cam 27 (on the drive shaft 6) by a spring 28, theends of which bear upon the sleeve 22 and yoke 23.

The upper periphery of the bore 17 is beveled to form a seat for theinlet valve 29 which is mounted and operated in the same manner as valve20 but by means of a cam 30 on the drive shaft 6. Since the air entersthe chamber 11 past inlet valve 29 in a compressed state and leaves saidchamber past exhaust valve 20 in a relatively expanded state the valve20 is made larger than the valve 29 and the upper portion of the bore 16is correspondingly enlarged, the bores 16 and 17 being otherwise thesame.

Correspondingly, the bore 18, connected to the upper portion of bore 16by a lateral passage 31, is larger than the bore '19, connected to theupper portion of the bore 17 by a lateral passage 32.

The compression chamber 2 is defined by the cylindrical wall 33, by thecylinder head 34 and by the upper surface of the compressor piston 9. Acheck valve is formed in the cylinder head as by the provision of acentrally perforated plate 35 the opening in which is closed by a disc36, urged toward the plate by the spring 37. The check valve permitspassage of air under pressure from the chamber 2 to the compressoroutlet 38.

The piston *9 is cut away at a plurality of points around its peripheryto form, with the seal ring described below, slots 39 through which aircan pass on the downward stroke of the piston, the slot walls beingbeveled inwardly toward the lower face of the piston as clearly shown inFIGS. 1, 2 and 3. The piston seal ring 40 has a cylindrical part andannular flanges 41, 42 spaced by a distance somewhat greater than thethickness of the piston periphery. On the downward (inlet) stroke of thepiston the upper surface thereof moves away from the under surface ofthe flange 41, permitting passage of air around the edge of flange 42,through the beveled slots 39 and between the piston and flange 41 intothe compression chamber 2 (FIG. 1). On the upward (compression) strokethe upper surface of the piston bears firmly against the under surfaceof flange 41 around the entire periphery of the piston, enabling thering 40 to act as a seal while the piston compresses the air and forcesit under compression past the check valve to the outlet 38 (FIG. 2.).The piston 9, seal ring 40, cylinder head 34 and plate 35 are preferablyso shaped and arranged that the volume of the chamber 2 is reducedsubstantially to zero at the end of the compression stroke.

The compressor outlet 38 communicates with the inlet of an air-cooledheat exchanger 43 which may be of any conventional type such astube-and-fin, while the outlet of the heat exchanger is connected by thepipe 44 to the lower end of the bore 19. A fan 45 is mounted on the endof the drive shaft 6 and is enclosed in cowling 46 arranged to enablethe fan to draw ambient air through the heat exchanger 43 and drive itpast the outside of the chamber 2, which may be provided with fins 47.An air intake opening 48 is formed in the wall of the crank case portion4 and is preferably provided with a dust filter 49. Said intake maymerely be open to ambient air, as shown, or may be connected by asuitable conduit to the space to be cooled, for recirculation of theair. The lower end of the bore 18 is connected to the space to be cooledby a pipe 50, which should be larger than the pipe 44.

In order to minimize vibration during operation it is desirable to mountcounter-weights 51 on the drive shaft 6 adjacent each of the eccentrics14, said counterweights being of a size and shape to balance kineticallythe eccentrics and the parts associated therewith. Shaft seals 52 areprovided each side of the cam 30 in order to prevent leakage of airunder pressure in the upper part of bore 17 through said bore into thecrank case. Leakage of low pressure air through bore 16 is relativelyunimportant so that special steps need not be taken to prevent it.

For simplicity of maintenance it is preferable that the bearings shouldall be pro-lubricated. The piston seal ring 40 is of a filled Teflontype, intended to run dry and having great durability.

In the cycle of operation, the air to be cooled enters the uppercylindrical part of the crankcase through the intake 48, being drawn inby upward movement of the piston 9, the periphery of which is tightlysealed against the lower surface of flange 41 on seal ring 40. When thepiston 9 reaches the top of its stroke (FIG. 2) the volume of chamber 2is nearly zero; thus, on the downward stroke, with valve 36 closed, theair in the crank-case is drawn through the slots 39 into the chamber 2until the latter attains its maximum volume--at the bottom of thestroke. As the piston moves upward again the air in the chamber 2 iscompressed and driven out past valve 36 into the compressor outlet 38,the air being at a somewhat elevated temperature corresponding to itscompression, and exceeding any normal ambient temperature The heated andcompressed air flows to and through the heat exchanger 43, where it iscooled somewhat without much pressure drop, and thence through pipe 44and bore 19, past valve 29, to the expansion chamber 11. Valve 29remains open for part of the stroke and then closes permitting expansionto take place. The closing point is computed so that at the end of theexpansion stroke the pressure in the cylinder is approximately ambient.Since the expansion chamber is formed in or carried by the compressorpiston, the expansion of air in chamber 11 is simultaneous with thecompression of another charge in chamber 2, and the force of expansion,urging the piston upward, serves to recoup a substantial part (e.g.,45%) of the energy required to compress the air above the piston anddrive the several moving parts. As the air expands, its drop in pressureis accompanied by a drop in temperature so that, at the top of thestroke, the chamber is filled with cool air at low pressure; the outletvalve 20 then opens (FIG. 2), and the cooled expanded air is driven outduring the downward stroke at low pressure through bore 18 and pipe 50to the space to be cooled. The ambient air, moved by fan 45, picks upsome heat on its passage through the heat exchanger 43 but is stillnormally capable of having some further cooling effect as it passes thefins 47 around the compression chamber 2.

As a matter of thermodynamics it might be preferable to mount the fandownstream from the compression chamber (as, at the right of FIGS. 1 and2), so that both the heat exchanger and the compressor would be cooledby air under suction, but the improvement in efiiciency from such anarrangement is seldom suflicient to justify the increased cost ofcowling and enlargement of the over-all dimensions of the device.

While a single-cylinder unit is shown and described herein as being apractical embodiment of the invention for eifectively cooling smallspaces, it will be understood that a plurality of cylinders (2, 3 ormore) could be coupled axially or otherwise for more heavy dutyinstallations. A 3 cylinder radial unit is illustrated diagrammaticallyin FIG. 5, each cylinder being substantially of the type described indetail herein and utilizing a common drive shaft, fan and heatexchanger, while master connecting rods 53 (corresponding to rods 15)for operating one piston are operatively coupled by links 54 to theother pistons.

In a small unit the drive shaft 6 may be actuated by a flexible shaftdrive from the vehicle engine fan belt, but a separate combustion orelectric drive may be used if desired. The source of power, being nopart of the present invention, is not shown. Typical performance of aunit substantially as shown and described calls for operation at a speedof 1000 rpm, with the 1.25 inch stroke giving a piston speed of 208feet/min. Assuming at least volumetric efliciency the air flow wouldthen be approximately 34 c.f.m. On a dry air basis, with air enteringthe expansion chamber at 115 F., the temperature drop would be 154 witha 3 to 1 expansion ratio. Assuming 70% adiabatic efiiciency, thetemperature drop is 108, representing a cooling load on a F. day of 65B.t.u./min., or .32 tons. Moisture in the air will raise the outlettemperature somewhat but the cooling capacity in B.t.u.s will remain thesame. Control may be efi ected simply for example, by providing a manualvalve (not shown) for bypassing part of the air flow around theexpansion cyclinder to reduce pressure at the expansion cylinder inlet.

What I claim is:

1. An air cycle cooling unit comprising, an air compression cylinder, apiston movable in said cylinder, an air expansion cylinder connected tosaid piston and movable therewith, a valve block located in andextending across the air expansion cylinder, means for supplying air tothe compression cylinder, a conduit including a heat exchangerconnecting the compression cylinder to the expansion cylinder, means forconducting air from the expansion cylinder to a space to be cooled, andmeans for reciprocating said piston and expansion cylinder to eflfectcompression in the compression cylinder and expansion in the expansioncylinder.

2. An air cycle cooling unit according to claim 1 in which the expansioncylinder is integral with the piston.

3. An air cycle cooling unit according to claim 2 which includes a driveshaft and at least one eccentric fixed on said shaft, and in which saideccentric is operatively connected to the expansion cylinder and piston.

4. An air cycle cooling unit according to claim 3 in which there are twoeccentrics operatively connected to the expansion cylinder and piston atdiametrically opposite points thereof.

5. An air cycle cooling unit according to claim 3 which includes aninlet valve controlling the admission of air to the chamber within theexpansion cylinder, a valve controlling the exhaust of air from saidchamber to the space to be cooled, and cams on the drive shaft foroperating said valves.

6. An air cycle cooling unit according to claim 5 in which the valvesare lift valves having stems lying in the same plane with the axis ofthe drive shaft.

References Cited in the file of this patent UNITED STATES PATENTS196,253 Root Oct. 16, 1877 1,495,663 Belluzzo May 27, 1924 2,415,618West Feb. 11, 1947 2,873,061 Kodra Feb. 10, 1959

